Heretofore, there has been known a gear device designed to output a rotational force at a rotational speed reduced with respect to an input rotational speed, by using an eccentric portion of a crankshaft to cause an externally toothed gear to be oscillatingly rotated while being meshed with internal teeth, as disclosed in WO 2009/119737 A1. As illustrated in FIG. 3, in the gear device disclosed in WO 2009/119737 A1, a through-hole 61c is formed in a central region of a carrier 61 having an end plate 61a and a basal section 61b, and a cylindrical body 63 for facilitating insertion of a cable is disposed in the through-hole 61c. The cylindrical body 63 has an intermediate portion formed with a groove 63a, and a retaining ring 65 is fitted onto the intermediate portion while being fitted into the groove 63a. One end of the cylindrical body 63 and the retaining ring 65 are clamped from opposite sides by the endplate 61a and the basal section 61b, so that the cylindrical body 63 is fixed to the carrier 61.
WO 2009/119737 A1 discloses another configuration designed to fix the cylindrical body using a sealing ring. As illustrated in FIG. 4, in this configuration, a sealing ring 69 is fitted into the groove 63a formed in the intermediate portion of the cylindrical body 63. The sealing ring 69 is pressed against and brought into close contact with an inner peripheral surface of the through-hole 61c in the end plate 61a, by an elastic force thereof, so that the cylindrical body 63 is fixed to the carrier 61.
In the configuration illustrated in FIG. 3, i.e., the configuration designed to fix the cylindrical body 63 to the carrier 61 using the retaining ring 65, one end of the cylindrical body 63 and the retaining ring 65 are clamped from opposite sides by the end plate 61a and the basal section 61b. For this purpose, in a production process of the gear device, before assembling the end plate 61a and the basal section 61b together to form the carrier 61, it is necessary to install the cylindrical body 63 to the carrier 61. Specifically, it is necessary to insert the cylindrical body 63 having the retaining ring 65 attached thereto, into the through-hole 61c in the basal section 61b, and then install the end plate 61a to the basal section 61b. Moreover, it is necessary to ensure dimensional accuracy of the carrier 61 and the cylindrical body 63, which raises a need for dimensional control for the carrier 61 and the cylindrical body 63. Therefore, the configuration illustrated in FIG. 3 has a problem that a gear device production operation becomes cumbersome and complicated. On the other hand, as to the configuration using the sealing ring 69 as illustrated in FIG. 4, the Patent Document 1 mentions that the sealing ring 69 is pressed against the through-hole 61c, and the cylindrical body 63 is fixed to the carrier 61 by an elastic force of the sealing ring 69. However, in reality, the cylindrical body 63 is liable to be displaced in an axial direction thereof, which causes a problem that the cylindrical body 63 is likely to drop off.